1. Field
Exemplary embodiments described herein relate to numerical aperture (NA) controlling units that control numerical aperture (NA), variable optical probes which include the NA controlling units, and depth scanning methods which use the NA controlling units.
2. Description of the Related Art
The demand for technologies relating to performing precise tomography on lower layers of human skin tissue and the demand for information relating to human skin tissue in the field of medical imaging are increasing. In particular, because many cancers originate in lower cells of the epithelium and are spread into cells of the hypodermis, in which blood vessels exist, if cancer can be detected at an early stage, injury caused by cancer can be greatly reduced. By using existing imaging technologies, such as magnetic resonance imaging (MRI), x-ray computed tomography (CT), ultrasonography, and the like, tomography may be performed on layers which are underneath human skin tissue when light penetrates into human skin tissue. However, because resolutions of devices for performing such imaging technologies are low, early stage cancer, in which a tumor is small, may not be detected. In contrast, by using optical coherence tomography (OCT) technologies that have been recently introduced, penetration depths of light into skin generally fall within the range of about 2 mm to about 3 mm and thus are relatively low as compared to corresponding penetration depths of existing imaging methods. Resolutions of devices used for performing OCT technologies are generally approximately ten times greater than the corresponding resolutions of ultrasound devices, and thus are relatively high as compared to the corresponding resolutions of devices used for performing other existing imaging methods. Thus, research relating to using OCT to detect early stage cancer in which a size of a tumor falls within the range of about 50 μm to about 100 μm is ongoing. However, because resolutions of devices for performing such OCT technologies are lower than the corresponding resolutions of microscopes, OCT technologies may not replace biopsies and histologies, which are actually used in detecting cancer.
Some OCT researchers have recently conducted research based on an ultimate goal of performing cancer diagnosis inside tissue in real-time without performing a biopsy by combining characteristics of OCT and high-resolution surface tomography, for example, by using confocal microscopy. However, microscopes are generally employed in conjunction with an optical system having a relatively high numerical aperture (NA) so as to realize a relatively high resolution in a horizontal direction, whereas an OCT device is generally employed in conjunction with an optical system having a relatively low NA which corresponds to a relatively uniform spot size in a depth direction, i.e., a relatively large depth of focus (DOF), so as to obtain depth information.